The detection and recognition capability can be improved by using infrared dual-band imaging to obtain more information.The application of multi-layer Diffractive Optical Elements (DOEs) in infrared dual-band optical system can correct the chromatic aberration and simplify the system structure.Compared with the single-layer DOEs,the multi-layer DOEs have higher diffraction efficiency in wide wave bandwidths.In this paper,the imaging characteristics of multi-layer DOEs are presented,and the design method is given.Based on which,an infrared dual-band hybrid diffractive-refractive optical system is designed.The diffraction efficiency of the double-layer DOE is higher than 98.5% in the working bands of 3.7 to 4.8 μm and 7.7 to 9.5 μm.The simulation result shows that the system has fine imaging quality,and the performance meets the optical system requirements.